Interferometric measuring devices perform measurements in tight cavities, for example, where a bundled measuring light is directed by suitable lighting optics onto an area of an inner surface, which is scanned, e.g., by moving a reference mirror in the direction of the reference arm. However, the area of the inner surface included in this scanning is relatively small. With such a measurement, it is also not easy to accurately determine the measurement point relative to the object. If such a measuring device is to be used in manufacturing, there may be disadvantages due to the measurement complexity.
Conventionally, to measure seat surfaces in valve-seat members, mechanical scanning devices have been used to scan the seat surface and/or the sealing area thereof, e.g., by rotating the valve-seat member. The roundness of the seat surface is determined from the scanning results and a good/bad evaluation is performed.